1. Field of the Invention
The invention generally relates to methods that may be used in performing joint surgery; with a particular embodiment of the invention being described, without limitation, in the context of knee arthroplasty. More particularly, with respect to knee arthroplasty, the invention relates to methods used to properly locate and guide instruments that resect bone in order to achieve a proper cut; and facilitate the proper location and installation of artificial femoral and tibial prosthetic components.
2. Brief Description of the Prior Art
Total knee arthroplasty involves the replacement of portions of the patellar, femur and tibia with artificial components. In particular, a proximal portion of the tibia and a distal portion of the femur are cut away (resected) and replaced with artificial components.
As used herein, when referring to bones or other body parts, the term xe2x80x9cproximalxe2x80x9d means closest to the heart and the term xe2x80x9cdistalxe2x80x9d means more distant from the heart. When referring to tools and instruments, the term xe2x80x9cproximalxe2x80x9d means closest to the practitioner and the term xe2x80x9cdistalxe2x80x9d means distant from the practitioner.
There are several types of knee prostheses known in the art. One type is sometimes referred to as a xe2x80x9cresurfacing typexe2x80x9d. In these prostheses, the articular surface of the distal femur and proximal tibia are xe2x80x9cresurfacedxe2x80x9d with respective metal and plastic condylar-type articular bearing components.
The femoral component is typically a metallic alloy construction (cobalt-chrome alloy or 6A14V titanium alloy) and provides medial and lateral condylar bearing surfaces of multi-radius design of similar shape and geometry as the natural distal femur or femoral-side of the knee joint.
One important aspect of these procedures is the correct resection of the distal femur and proximal tibia. These resections must provide planes which are correctly angled in order to properly accept the prosthetic components. In particular, the resection planes must be correctly located relative to three parameters: proximal-distal location, varus-valgus angle and flexion-extension angle.
U.S. Pat. No. 5,916,219 (hereby incorporated by reference) discloses an apparatus and method for tibial alignment which allows the independent establishment of two separate geometric planes to be used as a reference for the cutting of the tibial plateau during total knee arthroplasty.
Two separate frame assemblies with telescoping rods are attached to the tibia with a fixed relative angle between them, thereby allowing alignment with the mechanical axis of the bone. A cutting block is mounted on one of the assembly frames and is positioned against the tibia. Stabilizing pins are then placed in the cutting block, allowing the proper tibial plateau resection plane to be created.
The apparatus and method taught in the ""219 patent, while solving many prior art problems as indicated therein, has a few disadvantages. The alignment apparatus must be removed prior to performing resection. The device ratchets to discrete locations, preventing a smooth (hereinafter defined as an xe2x80x9cinfinitely adjustablexe2x80x9d) alignment. Further, the device can only be used to resect the tibia and cannot be used for femoral resection.
Recently, various computerized systems have been introduced to aid the practitioner during different surgical procedures. A typical, commercially available system is described in the attached Appendix. Such systems typically include multiple video cameras which are deployed above and around the surgical site; and a plurality of dynamic reference frame (DRF) devices, also known as trackers, which are attached to body parts and surgical instruments.
The trackers are generally LED devices which are visible to the cameras. Using software designed for a particular surgical procedure, a computer receiving input from the cameras guides the placement of surgical instruments.
The prior art instruments used for determining the correct planes for tibial and femoral resection in total knee arthroplasty are not well suited for use with computerized systems. The known tools utilize either intra-medullary alignment or extra-medullary alignment techniques and movement in three degrees of freedom is difficult or impossible. Moreover, in order to be useful with computer aided navigation systems, trackers must be attached to the tools. Existing tools do not permit or readily facilitate the attachment of trackers.
Although computer aided navigation systems are superior to unaided visual navigation by the practitioner, computers have known faults. As every computer user knows, any computer can crash or fail in such a way that it may take hours to repair. This is unacceptable during a surgical procedure. Therefore, it is necessary to provide a backup system of some kind so that the procedure may be completed without the failed computer.
It is therefore an object of the invention to provide methods, systems and tools for performing femoral and tibial resection and indeed, methods, systems and tools similarly useful in performing surgery on other joints (implicit in the objectives and description of the invention set forth herein, although reference to the femur and tibial resection is specifically made for the sake of illustration).
It is also an object of the invention to provide methods, systems and tools for femoral and tibial resection which allow location of a cutting guide relative to three parameters.
It is another object of the invention to provide methods, systems and tools for femoral and tibial resection which are infinitely adjustable.
It is still another object of the invention to provide methods, systems and tools for femoral and tibial resection which are adapted to be used with computer aided navigation systems.
It is also an object of the invention to provide tools which can be used for both femoral and tibial resection.
It is another object of the invention to provide methods, systems and tools for femoral and tibial resection which can be used without computer aided navigation systems should such a system fail during surgery.
In accord with these objects which will be discussed in detail below, the tools of the present invention (again, described in the context of knee surgery for illustrative purposes only), include anchoring devices for attachment to the femur and the tibia, a three-way alignment guide attachable to the anchoring devices and adjustable relative to three parameters, two embodiments of a resection guide attachable to the alignment guide and equipped with couplings for trackers, a plane probe for examining the resected plane, and apparatus for EM alignment of the resection guide in the event of a computer failure.
According to one aspect of the invention, the tibial anchoring device is specially designed to fit the triangular anatomy of the tibia. According to further aspects of the invention, the two resection guides both include rotatable pin guides to allow selection of anchoring pin location; one resection guide may be slotted and according to another embodiment of the invention, one is not slotted.
Further, according to one embodiment of the invention, the apparatus for visual EM alignment includes an EM rod and an EM alignment guide (sometimes referred to as an alignment handle). The EM rod is attachable to the EM alignment guide and the EM alignment guide is attachable to the cutting guide. The EM alignment guide contemplated by a further aspect of the invention has two ends, one of which as adapted for femoral alignment and the other of which is adapted for tibial alignment.
The methods of the invention include operating the computer aided navigation apparatus in the conventional manner including attaching one or more trackers to the bone to be resected; choosing a location for the anchoring device with or without guidance from the computer and installing the anchoring device; attaching the three-way alignment guide to the anchoring device; attaching a resection guide to the alignment guide; attaching one or two trackers to the resection guide; locating the resection guide with the aid of the alignment guide and the computer; fixing the resection guide to the bone with pins through the rotatable pin guides; and resecting the bone.
After the bone is resected, the resection plane probe may be attached to a tracker and moved about the resected plane to obtain feedback from the computer navigation system.
In the event of computer failure, the methods include attaching the EM alignment guide to the resection guide; attaching the EM rod to the EM alignment guide; and locating the resection guide by visual location of the EM rod rather than by feedback from the computer navigation system.
In accordance with the present invention, there is disclosed a method for aligning a resection guide relative to a patient""s bone during arthroplasty, the method including coupling an alignment guide to a patient""s bone, coupling a resection guide to the alignment guide, and positioning the resection guide along a translational path and along a plurality of rotational paths by manipulating the alignment guide.
In accordance with the present invention, there is disclosed a method for aligning a resection guide relative to a patient""s bone during arthroplasty, the method including coupling an alignment guide to a patient""s bone, coupling a resection guide to the alignment guide, and aligning the resection guide relative to the bone in three degrees of freedom by manipulation of the alignment guide, at least one of the degrees of freedom being rotational.